Transmissions utilising gear systems are, of course, well known and used in almost all industries. Generally, in order to engage one gear with another gear it is necessary that the gears have the same diametric pitch if they are of involute gear form. The same can be said for modulus as used in the metric system. In this description, the word modulus will be used to refer to the relationship between pitch and tooth diameter, even though they related to teeth or profiles of other involutes. Throughout this specification the words modulus will be used. If the gears have teeth of different modulus, it is generally not possible for the gears to engage and obey the fundamental law of rolling gears and transmit drive one to another.